It is the restaurant responsibility to keep its premises clean and dry. Imagine when I had food poisoning and shit / vomit in the restaurant, do I still need to "Pay" for the clean up. This is regardless if I got the food poisoning from the restaurant or not.
Paying is just a good will for the inconvenience that I have caused. If the guy is patron ... restaurant has a duty to take care of its patrons. If this guy is just a passerby, then the restaurant has the right to demand a cleaning fees.
However, if place is a kopitiam where public access is available, then sorry, the restaurant has to bear with it.
Race and IQ